test: Use fake timers for history compaction tests (#35573)

packages/cli/src/services/pruning/__tests__/workflow-history-compaction.service.test.ts

@@ -64,6 +64,16 @@ describe('WorkflowHistoryCompactionService', () => {
 	});
 
 	describe('startCompacting', () => {
+		beforeEach(() => {
+			// Set the system to a time that isn't 3 AM to avoid hitting the "trim once a day" window
+			const mockDate = new Date(2026, 10, 10, 1, 0, 0);
+			vi.setSystemTime(mockDate);
+		});
+
+		afterEach(() => {
+			vi.useRealTimers();
+		});
+
 		it('should start compacting if service is enabled and DB is migrated', () => {
 			const compactingService = new WorkflowHistoryCompactionService(
 				config,
@@ -194,4 +204,64 @@ describe('WorkflowHistoryCompactionService', () => {
 		// should still call recent history compaction
 		expect(optimizeHistoriesSpy).toHaveBeenCalled();
 	});
+
+	it('should trim if triggered at 3 AM with trimOnStartUp as false', () => {
+		const mockDate = new Date(2026, 10, 10, 3, 0, 0);
+		vi.setSystemTime(mockDate);
+
+		const compactingService = new WorkflowHistoryCompactionService(
+			{ ...config, trimOnStartUp: false },
+			globalConfig,
+			mockLogger(),
+			mock<InstanceSettings>({ isLeader: true, instanceType: 'main', isMultiMain: true }),
+			dbConnection,
+			mock(),
+			mock<EventService>(),
+		);
+
+		vi
+			// @ts-expect-error Private method
+			.spyOn(compactingService, 'optimizeHistories')
+			.mockImplementation((() => {}) as never);
+		const trimLongRunningHistoriesSpy = vi
+			// @ts-expect-error Private method
+			.spyOn(compactingService, 'trimLongRunningHistories')
+			.mockImplementation((() => {}) as never);
+
+		compactingService.startCompacting();
+
+		expect(trimLongRunningHistoriesSpy).toHaveBeenCalled();
+
+		vi.useRealTimers();
+	});
+
+	it('should not trim if triggered outside of 3 AM with trimOnStartUp as false', () => {
+		const mockDate = new Date(2026, 10, 10, 5, 0, 0);
+		vi.setSystemTime(mockDate);
+
+		const compactingService = new WorkflowHistoryCompactionService(
+			{ ...config, trimOnStartUp: false },
+			globalConfig,
+			mockLogger(),
+			mock<InstanceSettings>({ isLeader: true, instanceType: 'main', isMultiMain: true }),
+			dbConnection,
+			mock(),
+			mock<EventService>(),
+		);
+
+		vi
+			// @ts-expect-error Private method
+			.spyOn(compactingService, 'optimizeHistories')
+			.mockImplementation((() => {}) as never);
+		const trimLongRunningHistoriesSpy = vi
+			// @ts-expect-error Private method
+			.spyOn(compactingService, 'trimLongRunningHistories')
+			.mockImplementation((() => {}) as never);
+
+		compactingService.startCompacting();
+
+		expect(trimLongRunningHistoriesSpy).not.toHaveBeenCalled();
+
+		vi.useRealTimers();
+	});
 });